FIELD OF THE INVENTION
This invention relates to an optical position detection apparatus. More particularly, it relates to detection of tilting states, such as rolling or pitching states, by simplified optical means.
There are known a wide variety of this type of tilt meters. Typical of these is the structure of a dynamically tuned gyro disclosed in, for example, the Japanese Patent Kokai Publication No. 237313/1985, shown herein in FIG. 1.
In this FIG. 1, 1 is a casing substantially in the form of an inverted letter U. A frame 3 having a pair of ball bearings 2 at an axial center thereof is fitted within an inner wall la of the casing 1.
A stator 4a having a stator winding 4 is fixedly mounted on an inner wall 3a of the frame 3, and a rotor shaft 5 is rotatably mounted by an inner ball race 2a of each bearing 2.
The frame 3 is secured to an outer ball race 2b of each bearing 2. An annular hysteresis ring 7 is mounted on the outer periphery of a generally U-shaped end cap 6 which is secured to the inner ball race 2a and a lower extremity 5b of the rotor shaft 5. A motor rotor 8 is constituted by the end cap 6 and the hysteresis ring 7, whereas a spin motor 9 is constituted by the stator 4a and the motor rotor 8.
On the top of the rotor shaft 5, a gyro rotor 13 is mounted by means of a hinge unit 12 consisting of a gimbal 10 and a spring member 11. This gyro rotor 13 is constituted by a ring having a substantially U-shaped cross-section. A ring magnet 14 is fixedly mounted on the inner wall of the gyro rotor 13.
A sensor ring 15 is provided at the lower extremity of the gyro rotor 13 and a sensor coil 16 is mounted upright at a position on the frame 3 which is in register with the sensor ring 15.
A torquer coil 17 constituting a torquer unit is provided upright on the upper surface of the frame 3 and has its distal end positioned within the inside of the gyro rotor 13 and in register with the ring magnet 14.
A terminal 20 is provided by means of an insulator 19 on a terminal plate 18 mounted on the lower extremity of the casing 1.
The above-described dynamically tuned gyro operates as follows: When the spin motor 9 is actuated in the state of FIG. 1, the rotor shaft 5 is rotated at an elevated speed for rotating the gyro rotor 13 at an elevated speed by means of the hinge unit 12.
Should a tilt be caused to gyro rotor 13, the tilt state is sensed by sensor coil 16. A control current is caused to flow through torquer coil 17, whereby a force proportional to the product of the magnetic flux through the gyro rotor 13 and the ring magnet 14 and the control current through the torquer coil 17 is produced for controlling the position of the gyro rotor 13.
The above described gyro rotor suffers from the following disadvantages.
Since the tilting state of the rotor rotated by the electric motor is sensed by the magnet and the sensor coil, the gyro has an extremely complex mechanical structure and hence is difficult to assemble it to lower its production costs.
On the other hand, only the tilting angle within a narrow range can be sensed because the angular velocity or the tilting angle that can be sensed is limited by the capacity of the torquer unit and also because the angle that can be sensed by the torquer unit is small. An excessive current flowing through the torquer unit tends to destroy the torquer unit.